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Target release	1.0
Epic
Document status
Document owner	Alexander Feldt
Designer	Zsolt Erdei
Developers	Clemens Cramer
QA	Tita Petre

Goals

Align BLF and Extension behavior for PFKs on Snom desk phones by using XML definitions instead
- Improve user experience
- Improve performance

Background and strategic fit

BLF is a valuable feature for Snom customers, like enterprises who are looking to assist in connecting their customers to a live, available person as well as save business phone use time. Overall, it enables businesses to streamline their communication and better serve customers. BLF aka Extension monitoring has been utilized in numerous ways by businesses using Snom phone systems with multiple extensions. The current implementation appears to be kind of duplicated, but with a few little differences and erroneous behaviour.

Assumptions

Use case#1: A secretary's phone shall display the call status of the boss's line, allowing the secretary to know whether the boss is on a phone call or not. This will enable the secretary to make the decision to put the new caller on hold or let them through to the boss.
Use case#2: Call centers and customer support groups have also a need for BLF: it enables employees to see if their colleagues are free to take a support call or if their supervisor is on another line and unable to help another customer.
Use case#3: BLF is needed by teams working on a specific project: supervisors can monitor team members' extensions and vice versa so all team members are aware of each other's current status.

Requirements

#

Requirement title

Functionality

Importance

Notes

1

D8XX_BLF-XML_FR-1

On D8xx IP phones, any PFK (programmable function key - physical or virtual) can be assigned to a function, which allows monitoring state changes of the configured SIP extension on another IP phone. This function shall be called "BLF-XML". The following state changes shall be visualized:

monitored SIP extension is in idle mode => idle
monitored SIP extension seizes a line => busy
monitored SIP extension receives an incoming call => ringing
monitored SIP extension places an outgoing call => busy
monitored SIP extension dials or accepts an incoming call => busy

Must Have

This means, that the D8xx phone acts as a User Agent Client (UAC) and the IP phone of the monitored extension acts as User Agent Server (UAS).

2

D8XX_BLF-XML_FR-2

On Snom IP phones acting as UAS, any SIP extension having an active subscription of its state changes, shall sent a notification SIP message (NOTIFY) to the UAC, at least when one of the following state changes occur:

from any state => idle
from any state => trying
from any state => early
from any state => busy

Must Have

Fully implemented

3

D8XX_BLF-XML_FR-3

The assignment shall be configured either manually via web user interface (WUI) and/or phone user interface (PUI), and automatically via auto-provisioning (HTTP/TFTP setting server), SRAPS, or remote management (TR-069).

Must Have

Fully implemented

4

D8XX_BLF-XML_FR-1-1

On D8xx series, during an active subscription, state changes of the monitored SIP extension shall be visualized on both, PFK LED and PFK label.

Must Have

Fully implemented

5

D8XX_BLF-XML_FR-1-1-1

The PFK LED behaviour and colour shall be according to this table

state	idle	ringing	busy
LED behaviour	off	blinking	on
LED colour	-	red	red

Must Have

Fully implemented

6

D8XX_BLF-XML_FR-1-1-2

The PFK label shall be composed of 3 areas:

(A) icon area	(B) name area
	(C) state area

Must Have

Fully implemented

7

D8XX_BLF-XML_FR-1-1-2-1

The label icon area (A) shall contain the following distinguishable graphical symbol, representing the state

State	idle	ringing	busy
Description	person with a handset	person with a handset plus an arrow (pointing towards the handset)	person with a handset and 2 sound waves (heading away from the handset)
Graphical symbol
Colour	white	red	red

Must Have

Fully implemented

8

D8XX_BLF-XML_FR-1-1-2-2

The label name area (B) shall contain the following text representing the display name or number (configurable) of the monitored / calling party

state	idle	ringing	busy
roles	Monitored party	Calling party > monitored party	Calling party <> monitored party
text	101 or Alex	102 > 101 or Alice > Alex	102 <> 101 or Alice <> Alex
text colour	white	white	white

Must Have

Partly implemented

9

D8XX_BLF-XML_FR-1-1-2-3

The label state area (C) shall contain the following text representing the state

state	idle	ringing	busy
text	idle	ringing	busy
colour	white	white	white

Must Have

Fully implemented

User interaction and design

User interaction

Protocols

Design reference

UAS

UAC

State

UAS => UAC

UAC

Figma

Screenshot

does nothing

Idle

seizes a line

does nothing

trying

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full"
	entity="sip:101@...">
	<dialog id="..." >
		<state>trying</state>
	</dialog>
</dialog-info>

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full"
	entity="sip:101@...">
	<dialog id="..." >
		<state>trying</state>
	</dialog>
</dialog-info>

hangs up

does nothing

terminated

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full"
	entity="sip:101@192.168.245.1">
	<dialog id="..."
		direction='initiator'
		call-id='...'
		local-tag=""
		remote-tag="">
		<state>terminated</state>
		<local>
			<identity display="B">sip:101@...</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
			</target>
		</local>
	</dialog>
</dialog-info>

incoming call ringing

does nothing

early

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full" entity="...">
	<dialog
		id="..."
		direction='recipient'
		call-id='...'
		local-tag="..."
		remote-tag="...">
		<state>early</state>
		<local>
			<identity display="B">
				sip:101@...
			</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
			</target>
		</local>
		<remote>
			<identity display="C">
				sip:102@...
			</identity>
			<target uri="sip:102@..."/>
		</remote>
	</dialog>
</dialog-info>

incoming call accepted

does nothing

confirmed

NOTIFY
...
<?xml version="1.0"?>
<dialog-info
	xmlns="urn:ietf:params:xml:ns:dialog-info"
	version="..."
	state="full"
	entity="sip:101@...">
	<dialog
		id="..."
		direction='recipient'
		call-id='...'
		local-tag="..."
		remote-tag="...">
		<state>confirmed</state>
		<local>
			<identity display="B">sip:101@...</identity>
			<target uri="sip:101@...;line=...">
				<param pname="x-line-id" pval="0" />
				<param pname="+sip.rendering" pval='yes' />
			</target>
		</local>
			<remote>
				<identity display="C">sip:102@...</identity>
				<target uri="sip:102@..."/>
			</remote>
	</dialog>
</dialog-info>

Questions

Below is a list of questions to be addressed as a result of this requirements document:

Question	Outcome
(e.g. How we make users more aware of this feature?)	Communicate the decision reached

Not Doing

List the features discussed which are out of scope or might be revisited in a later release.